CN-122025779-A - Local high-concentration in-situ polymerized gel electrolyte and application thereof in lithium metal battery

CN122025779ACN 122025779 ACN122025779 ACN 122025779ACN-122025779-A

Abstract

The invention provides a local high-concentration in-situ polymerized gel electrolyte and application thereof in a lithium metal battery, belongs to the technical field of lithium batteries, and aims to solve the technical problems of narrow voltage window and poor cycling stability of polyether-based electrolytes. The in-situ polymerized gel electrolyte is obtained by in-situ polymerization reaction of a precursor solution, wherein the precursor solution comprises the following raw materials of a cyclic ether polymerization monomer, an epoxy ether fluorinated derivative diluent, a plasticizer, an additive, an initiator and lithium salt, wherein the epoxy ether fluorinated derivative diluent refers to a fluorinated derivative in which a substituent on a carbon atom of the epoxy ether is hydrogen, fluoro, polyfluoroalkyl or perfluoroalkyl, and at least one substituent is perfluoroalkyl. The gel electrolyte has wide voltage window and good cycling stability. Meanwhile, after the diluent is added, the viscosity of the polymeric precursor is low, the wettability is good, and the preparation process is simple.

Inventors

HUO FENG
WANG LIWEI
FAN HAILIN
CAO XIAOJU
GAO WENCHAO
LIU YANFEI
FENG SHIHAO
ZHAO LIANGJU

Assignees

郑州中科新兴产业技术研究院
龙子湖新能源实验室

Dates

Publication Date: 20260512
Application Date: 20260211

Claims (10)

1. The local high-concentration in-situ polymerized gel electrolyte is characterized by being obtained through in-situ polymerization reaction of a precursor solution, wherein the precursor solution comprises the following raw materials of a cyclic ether polymer monomer, an epoxy ether fluorinated derivative diluent, a plasticizer, an additive, an initiator and lithium salt, wherein the epoxy ether fluorinated derivative diluent refers to a fluorinated derivative in which a substituent on a carbon atom of an epoxy ether is hydrogen, fluorine, polyfluoroalkyl or perfluoroalkyl, and at least one substituent is perfluoroalkyl.
2. The local high-concentration in-situ polymerized gel electrolyte according to claim 1, wherein the concentration of each component in the precursor solution is 30-70wt% of cyclic ether polymerized monomer, 9-50wt% of epoxy ether fluorinated derivative diluent, 2-30wt% of plasticizer, 0.5-10wt% of additive, 0.5-20wt% of initiator and 10-40wt% of lithium salt.
3. The locally high concentration in situ polymerized gel electrolyte of claim 2, wherein the mass ratio of the cyclic ether-based polymerized monomer to the epoxy ether-based fluorinated derivative diluent is 1-5:1.
4. The local high-concentration in-situ polymerized gel electrolyte according to claim 3, wherein the cyclic ether type polymer monomer is any one or two or more of 1, 3-dioxolane, 1,3, 5-trioxane, 1, 3-dioxane, 1, 4-dioxane, propylene oxide, tetrahydrofuran, methyltetrahydrofuran and tetrahydropyran, and the epoxy ether group fluorinated derivative diluent is any one or two or more of 4- (trifluoromethyl) -1, 3-dioxolane, 2-bis (trifluoromethyl) -1, 3-dioxolane, 4, 5-tetrafluoro-2, 2-bis (trifluoromethyl) -1, 3-dioxolane and 2-trifluoromethyl-2- (2, 2-trifluoroethyl) -1, 3-dioxolane.
5. The localized high concentration in situ polymerized gel electrolyte of claim 1, wherein the plasticizer is any one or two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, and propyl acetate.
6. The localized high concentration in situ polymerized gel electrolyte of claim 1, wherein the additive is any one or two or more of fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, acrylsultone, lithium difluorophosphate, 1, 3-propane sultone, tris (trimethylsilane) phosphate, 4-propyl- [1,3] -dioxolan-2-one, lithium tetrafluoroborate, lithium oxalate borate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and lithium nitrate.
7. The locally high concentration in situ polymerized gel electrolyte of claim 1, wherein the initiator is any one or two or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium difluorosulfimide, aluminum triflate, tin triflate, stannous octoate and azobisisobutyronitrile.
8. The locally high concentration in situ polymerized gel electrolyte of claim 1, wherein the lithium salt is any one or two or more of lithium bis (trifluoromethanesulfonyl) imide, lithium perchlorate, lithium bis (oxalato) borate, lithium difluorodioxaoxalato phosphate, lithium difluorophosphate, and lithium hexafluoroarsenate.
9. Use of a locally high concentration in situ polymerized gel electrolyte according to any of claims 1 to 8 in a lithium metal battery, comprising the steps of: (1) Under the protection of inert gas, uniformly mixing a cyclic ether polymerization monomer and lithium salt to obtain a mixed solution A; (2) Uniformly mixing an epoxy ether fluorinated derivative diluent, an additive, a plasticizer and an initiator to obtain a mixed solution B; (3) Adding the mixed solution A into the mixed solution B to obtain a precursor solution; (4) And injecting the precursor solution into the battery without the injected solution, then assembling the battery, and placing the battery and carrying out polymerization reaction to obtain the lithium metal battery containing the gel electrolyte.
10. The use of a locally high concentration in situ polymerized gel electrolyte in a lithium metal battery according to claim 9, wherein the temperature placed in step (4) is 25-60 ℃ for a period of 6-168 h.

Description

Local high-concentration in-situ polymerized gel electrolyte and application thereof in lithium metal battery Technical Field The invention belongs to the technical field of lithium batteries, and particularly relates to a gel electrolyte. Background In recent years, development of electric automobiles has put higher demands on key performance indexes such as energy density, safety, service life and the like of lithium ion batteries. The solid-state lithium battery adopts the solid electrolyte to replace the traditional liquid electrolyte, has the advantages of high safety, compatibility with high-capacity anode and cathode and the like, and is considered to be the most competitive solution for breaking through the performance bottleneck of the traditional liquid lithium ion battery in the future. In-situ polymerization is one of the easiest strategies for realizing commercial application of solid-state lithium metal batteries at present, the polymerization process is simple, and the polymerization reaction occurring in the battery can realize close contact between an electrode and an electrolyte, so that the interface impedance is reduced, and the lithium metal battery shows excellent electrochemical performance. The most common polymeric monomers are epoxy ethers, represented by 1, 3-Dioxolane (DOL). Epoxy ether solvents generally have low viscosity characteristics, facilitate in situ polymerization of the precursor electrolyte to infiltrate the separator and electrodes, and have significant stability relative to lithium metal, which has been widely studied in recent years. However, the terminal hydroxyl groups and ether oxygen chains of the polyether-based electrolyte exhibit intrinsic instability at high potential, poor oxidation resistance, a narrow voltage window, and side reactions are easily generated to affect cycle performance. Meanwhile, unpolymerized monomers remain in the in-situ polymerization process and are easily oxidized and decomposed under high pressure, so that the cycle performance is further deteriorated. In order to overcome the problems, the interface stability can be improved and the voltage window and the cycling stability can be improved by optimizing the method of in-situ polyelectrolyte components. The Chinese patent application CN118553996A utilizes dopamine modified glass fiber, and then synthesizes the PDOL-based polymer gel electrolyte modified by the silane coupling agent through in-situ polymerization on the modified glass fiber, so that a series of problems of low ionic conductivity, low lithium ion migration number and poor electrochemical stability of a PDOL system are greatly improved. However, modifying the glass fiber increases the manufacturing process and production cost. The Chinese patent application CN119742439A adopts deep eutectic solution as plasticizer, and the obtained high-voltage resistant in-situ polymerization solid electrolyte has the excellent characteristics of wide electrochemical window, high ionic conductivity, high mechanical strength, good flame retardance, wide-temperature applicability and the like, and can be suitable for a high-voltage system with the voltage of more than 4.6V. However, one of the main components of the deep eutectic solution is nitrile solvent, and the too high viscosity affects the wettability of the electrode and has stronger toxicity. Therefore, it is necessary to design an in-situ polymerized gel electrolyte which can form a stable solid electrolyte interface film (SEI) on the surface of an electrode, has less monomer residue, wide voltage window, good cycle performance, good wettability of a polymerization precursor and simple process. Disclosure of Invention Aiming at the technical problems of narrow voltage window and poor cycle stability of polyether-based electrolyte, the invention provides a local high-concentration in-situ polymerized gel electrolyte and application thereof in a lithium metal battery, and an epoxy ether-based fluorinated derivative is constructed by introducing electron-withdrawing fluorine or polyfluoro or perfluoroalkyl functional groups on the C site of epoxy ether. The electron-withdrawing fluorine group or the polyfluoroalkyl group or the perfluoroalkyl group can prevent ring-opening polymerization, reduce solvation capacity, and can be introduced into an in-situ polymerization gel electrolyte as a diluent to keep a close coordination structure of solvent molecules and anions and lithium ions in a local environment so as to form the local high-concentration gel electrolyte. The solvation structure in the gel electrolyte is mainly anions, and the Contact Ion Pairs (CIPs) and the aggregation ion pairs (AGGs) are dominant, so that a more stable interface protection layer rich in inorganic matters can be formed on the surface of the electrode, the oxidation resistance is enhanced, the oxidative decomposition of electrolyte is inhibited, and the high-voltage resistance is improved. In particular